Coated metallic sheet



Oct. 7, 1941. KRAMER 2,258,327

COATED METALLIC SHEET Original Filed April 24, 1957 Jfce/ fling.

Z/flc- 77/7 LeadA//0y Zinc Z inc Sheet 3 4 5 Zinc fikrrouJ-Z/hc ,4//0y 5INVENTOR Andre/4&4 Kramer BY 44 ATTORNEY Patented Oct. 7, 1941 UNITEDSTATE COATED METALLIC SHEET Andrew A. Kramer, Kansas City, Mo.

Original application April 24, 1937, Serial No. 138,813. Divided andthis application August 25, 1937, Serial No. 160,802

6 Claims. (Cl. 29-181) My invention relates to coated metallic sheetsprovided with zones in which the same can be bent .without damaging thecoating. This is a division of my co-pending application Serial No.138,813, filed April 24, 1937.

A diiiiculty that has always existed in the utilization of galvanizedmetal sheets has been that when such sheets, that had a heavy coat ofgalvanizing, were bent, the coating of galvanizing at the bend wouldcrack and tend to flake, or peel off. As a result, even though the sheetas a whole was provided with a heavy galvanized coating over its entiresurface before being fabricated, the bending of the sheet to form aflange, of a seam, would damage the galvanized coating on the sheet soseriously. that it would render the coating partially ineffective, wherethe bends required to form the flanges, or seams, were made, andconsequently the advantage of the heavy galvanized coating on the sheetwas largely lost. This was true, because, although the remainder of thesheet might be well coated and would not in any manner corrode, thatportion in which the galvanized coating was caused to be damaged by thebending, would be hardly any better than an uncoated sheet, as far asresistance to oxidation, or other corrosion, is concerned. Attempts havebeen made to overcome this difficulty by galvanizing by a hot dippingprocess, after fabrication,

but this entails many difliculties and requires very expensive equipmentand is substantially impossible to successfully perform, where largesheet metal sections, such as tanksections, are fabricated and are to beprotected from oxidation and other corrosion. It is th principal purposeof my invention to provide a sheet that is so treated before bending,that the bending will not injure the protective metallic coating on thesame, even though a heavy coat of the protective metallic coating may beprovided, and to provide a new and improved coated sheet that isprovided with bending zones, in which bending can take plate at rightangles, or even to the extent of doubling the sheet back on itself andforming a seam, without doing any damage to the metallic protectivecoating on the sheet. These zones may be made of any extent desired,and, while, preferably, only being provided at certain defined portionsof the sheet, can extend over substantially the entire sheet, or overthe entire sheet, if such is desirable.

The addedmetal can be applied anywhere desired on the sheet, in anyconfiguration, or in any desired area and in any desired manner. It canbe applied by contacting a solid piece of the metal, that is to beadded, with the sheet and brushing, or spreading, with any desiredimplement, or can be applied in a finely divided powdered form, with anydesired spraying, spreading, or sprinkling means, or can be applied withsuitable means, such as a metal spray gun, in a molten condition. Themetal that is applied must alloy with the zinc on the sheet to form aductile, or flexible, coating on the sheet in the bending zone. It mustbe applied while the spelter, or

zinc, is still in a molten state after passing through the galvanizingbath, and cannot be satisfactorily applied by re-heating of the sheets,

because buckling of the sheets and oxidation of the galvanizing coatingwould then occur.

Other objects and advantages of my invention will appear as thedescription of my invention proceeds. I desire to have it understood,however, that I do not intend to limit myself to the particular detailsdescribed, except as defined in the claims.

In the drawing:

i Fig. 1 is a fragmentary sectional view on a greatly magnified scale,showing one form of my coated metallic sheet, and

Fig. 2 is a similar view partly broken away. showing another form of myimproved coated sheet.

In making galvanized sheets, this is usually done by a hot submersionprocess, or dipping process, the metallic sheet of steel being passedthrough a bath of spelter, which is made up'of, principally, zinc,although very small quantities of other metals are present, the bestgrade of spelter being about 99.5% zinc, and may contain very smallfractional percentages of cadmium, or

lead, and poorergrades of spelter ranging down to about 99% of zinc,with an increase in the lead,

or cadmium content, as the case may be. As the melting point of the bestgrade of spelter is near 830 F., the bath for galvanizing is usuallykept at a temperature between 840 F. and 850 F. As a result of passingthe sheet through this bath, the temperature of the sheet, immediatelyafter it leaves the bath, is above that of the melting point of zinc, orat about the melting point of zinc, which would be about 830 F.

When a sheet is galvanized, zinc in the galvanizing bath alloys itselfwith the iron of the steel in the sheet, and forms a very thin layer ofa ferrous zinc ,alloy immediately adjacent the steel of the sheet.Inasmuch as this alloy has a much higher melting point than the spelter.or zinc, this immediately sets and thus prevents any further alloyingaction between the zinc and iron of the steel, the remainder ofthe'spelter forming a coating of almost pure zinc overlying the coatingof zinc-iron alloy on the sheet. This outer coating of zinc varies inthickness considerably, depending upon how it is applied to the sheet.Sheets are provided with a heavy coating of galvanizing by repeateddipping, or running of the sheets through the galvanizing bath. -Tlnezinc coating, of course, does not have the tensile strength of thesteel, nor the flexibility of the steel, and consequently when the sheetis bent the tendency is for the coating, particularly on the outer sideof the bend in the sheet, to break apart, or crack, at least down to thezinc-iron alloy that forms the innermost coating sheet.

In the making of my improved sheets, I apply an additional metal theretoimmediately after the sheets have emerged from the pot, or bath, inwhich the molten spelter is located, and through which the sheets havebeen passed, the coat of metal being applied, preferably, at the placewhere bending is to take place in the-sheet when it is to be fabricated,and being applied before the molten metal of the galvanizing bath hasset on the sheet. The metal can be applied by rubbing a bar of the metalon the sheet, or using pulverized metal, which is applied to the sheetby brushing or otherwise. The metal that is to be applied must becapable of alloying with the zinc on the sheet to form a ductile, orflexible, coating on the sheet. Any non-ferrous metal that has a lowenough melting point and will alloy with zinc to form a flexible, orbendable, or ductile, coating on the sheet, can be utilized. I prefer toapply lead, or tin, or a solder made up of lead and tin, or what isknown as an aluminum solder made up of tin and aluminum, to the sheetimmediately after it leaves the galvanizing bath.

The application can be done by merely rubbing a bar, or block, or solidpiece, of the metal across the sheet where it is desired to provide thealloy coating, spreading the saineby wiping or brushing means of anydesired character. It can be applied in a finely divided powdered stateand brushed, or spread out, if this is desired, or it may be applied ina finely divided form by spraying it in a finely divided solid, orpowdered, form on the zone on which it is desired to form the alloy, orit can be applied in a finely divided molten state by a suitable metalspray gun, or spraying apparatus.

The additional metal that is thus applied to form an alloy with thezinc, is applied in relatively small quantity in as finely divided andwidely spread out condition as possible, it being, of course, necessarythat suflicient of the alloying metal be applied, that the alloy will beformed throughout the zone in which it is desired to provide a ductile,or flexible, coating that will withstand the bending of the sheetwithout cracking, or breaking, of said coating. The portion of thecoating that needs the greatest flexibility is, of course, that nearestthe outer surface, because it will be subjected to the greatest tension,or compression, in bending. However, it is very desirable to have thischaracteristic of flexibility, or ductility, extend as far into thecoating as possible. The important feature of my invention is thealloying ofthe zinc with the tin, or with the on the by applying suchmetals as lead ortin, or lead tin solder, at temperatures lower thanthat existing immediately after the sheets leave the galvanizing bath,by adding a flux to the metal, or solder.

It has been found that in sheets made as herein described, a heavycoating of galvanizing so plete sheet, should this be found to beadvantageous, and that any such areas, or zones, of bending in anyconfiguration can be provided with the bendable, or flexible, .alloy, asmay be found desirable or necessary. It is, of course, to be understoodthat the application of the additional metal to the hot sheet, leavingthe galvanizing bath, can only be performed after the last passage ofthe sheet through such a bath, where it is passed through a bath morethan once, or through a series of galvanizing baths.

The added metal that forms the flexible alloy with the zinc maybe'applied on one or both sides of the sheet, as may be found desirableor necessary. In case only one side of the sheet is to be treated so asto obtain a flexible coating thereon in a bending zone, it would, ofcourse, be necessary to apply the additional metal, forming the alloywith the zinc, to that side of the sheet that will be on the outside ofthe bend, as that will be the coated surface that will be put under thegreatest tension and be the most liable to crack, or break, when thesheet is bent.

In Fig. 1 is shown a coated sheet that has a body portion 3 of steel, orsimilar sheet material, the ferrous zinc alloy coating that existsadjacent the steel of the sheet being indicated thereon by the numeral4, the zinc coating by the numeral 5, and the zinc-tin-lead alloycoating being indicated by the'numeral 6. In this form of the inventi onthe coating of zinc-tin-lead alloy extends over the entire area of thesheet. In Fig. 2 a modification is shown, in which the various coatingsare indicated by the same numerals. It will be noted, however, that inthe form of the in My improved coated sheets can also be made ventionshown in Fig. 2 the zinc-tin-lead alloy coatingis applied only tocertain areas, or zones, of the sheet, terminating at 1, these being thebending zones, or other zones in which the fabrication takes place. Thezinc-tin-lead alloy merges into the zinc coating at the boundary 1 ofthis zone and the major portions of the sheet have the zinc coatingexposed, on the side of the zone adjacent the steel body portion of thesheet,

an intermediate zone of substantially pure zinc, and an outer flexiblezinc alloy zone extending to the exposed surface of said coating, saidflexible alloy containing a relatively small quantity of a non-ferrousmetal having a lower melting point than zinc and a relatively largequantity of zinc, said outer zone having a suflicient percentage of zinctherein to retain the corrosion resisting characteristics of a zinccoating at the exposed surface thereof. 7 Y

2. A steel sheet having a protective coating thereon comprising an innerferrous zinc alloy zone adjacent the steel body portion of the sheet, anintermediate zone of substantially pure zinc, and an outer flexible zincalloy zone extending to the exposed surface of said coating, saidflexible alloy containing a relatively small quantity of lead and tinand a relatively large quantity of zinc, said outer zone having asufiicient percentage of zinc therein to retain the corrosionresistingcharacteristicsof a zinc coating at the exposed surfacethereof.

3. A galvanized metallic sheet having a bending zone having a thickcoating of zinc and a flexible zinc alloy coating overlying said zinccoating forming the exposed surface of said bending zone, said alloycontaining a relatively small quantity of a non-ferrous'metal having alower melting point than zinc and a relatively large quantity of zinc,said flexible coating having a suflicient percentage of zinc therein toretain the corrosion resisting characteristics of a 3 tain the corrosionresisting characteristics of a zinc coating at the exposed surfacethereof.

' teristics of a zinc coating at the exposed surface 5. .A steel sheethaving portions thereof coated with a zinc galvanizing coating,comprising an inner zone of an alloy of iron and zinc-and an outer zoneof zinc only, and other portions thereof coated with a coatingcomprising an inner zone of an alloy of zinc and iron, an intermediatezone of substantially pure zinc and an outer zone of a flexible zincalloy, said alloy containing a relatively small quantity of anon-ferrous metal having a lower melting point than zinc and arelatively large quantity of zinc, said flexible coating having asufficient percentage of zinc therein to retain the corrosion resistingcharacthereof, there being the same quantity of zinc per unit of areaover all portions of said sheet.

6. A steel sheet having portions thereof coated with a zinc galvanizingcoating only, and having bending zones coated with a zinc galvanizingcoating and a flexible zinc alloy coating that overlies said zincgalvanizing coating and forms.

the exposed surface of said bending zones, said zinc coating beingthinner where said alloy overlies the same than where said zinc coatingalone is employed, there being substantially the same quantity of zincper unit of area over all the portions of. said sheet, said alloycomprising zinc, lead and tin throughout its thickness, and hav-, ing a.percentage of zinc therein at its exposed 0 surface sufllcient to retainthe corrosion resisting characteristics of zinc at said surface.

ANDREW A. KRAMER.

